Corrections for a/an in code comments and documentation
diff --git a/Lib/lib-tk/Tkinter.py b/Lib/lib-tk/Tkinter.py
index cc657fa..e825afa 100644
--- a/Lib/lib-tk/Tkinter.py
+++ b/Lib/lib-tk/Tkinter.py
@@ -1252,7 +1252,7 @@
         # time field: "valid for events that contain a time field"
         # width field: Configure, ConfigureRequest, Create, ResizeRequest,
         # and Expose events only
-        # x field: "valid for events that contain a x field"
+        # x field: "valid for events that contain an x field"
         # y field: "valid for events that contain a y field"
         # keysym as decimal: KeyPress and KeyRelease events only
         # x_root, y_root fields: ButtonPress, ButtonRelease, KeyPress,